Recent literature on dense wavelength division multiplexing (“DWDM”) networking [1-5] has shown that as traffic traverses more number of hops, it suffers a higher blocking probability than traffic with less number of hops. This causes ‘unfairness’ among the different classes of service characterized by the number of hops between the source node and the destination node. In [5], the technique of protection threshold is used, where the single-hop traffic is assigned an idle wavelength only if the number of idle wavelengths on the link is at or above a given threshold. In [3], the Traffic Classification and Service method is introduced to optimize the fairness problem, where all the available wavelengths are divided into a number of wavebands, and preference is given to multi-hop traffic. Thus, the blocking probability of multi-hop traffic is lowered at the cost of an increase in the blocking probability of single-hop traffic, as well as a decrease in the traffic carrying capacity of the network. An alternative to the Traffic Classification and Service has been proposed in [6] that requires connection request to a waveband of a lower class should all the wavelengths reserved for its own class be fully occupied. Further, [7] has shown that bumping multi-hop traffic from its own class to a lower class will result in a precipitous drop in throughput under heavy load conditions. Reference [8] proposes an algorithm that solves the fairness problem under normal load condition by using downward overflow and switching to a fixed route, pre-assigned wavelengths for all source-destination pairs under heavy load conditions.
Under normal conditions, the carried traffic or the throughput of a network increases as the incident connection requests increase. However, if the network is congested, the carried traffic will remain constant or even decrease as the incident traffic increases [9].